The present invention relates to downhole tools and techniques used to radially expand a downhole tubular into sealing engagement with a surrounding tubular. More particularly, this invention relates to a technique for forming a downhole tubular patch inside a perforated or separated tubular utilizing a conventional interior tubular and a tool which forms an upper seal and a lower seal above and below the region of the perforation or separation. The invention also involves a tubular expander for expanding a downhole tubular, and a patch installation and tubular expander method.
Oil well operators have long sought improved techniques for forming a downhole patch across a tubular which has lost sealing integrity, whether that be due to a previous perforation of the tubular, high wear of the tubular at a specific downhole location, or a complete separation of the tubular. Also, there are times when a screened section of a tubular needs to be sealed off. A tubular patch with a reduced throughbore may then be positioned above and below the zone of the larger diameter tubular which lost its sealing integrity, and the reduced diameter tubular then hung off from and sealed at the top and bottom to the outer tubular. In some applications, the patch may be exposed to high thermal temperatures which conventionally reduce the effectiveness of the seal between the tubular patch and the outside tubular. In heavy oil recovery operations, for instance, steam may be injected for several weeks or months through the tubular, downward past the patch, and then into a formation.
U.S. Pat. No. 5,348,095 to Shell Oil Company discloses a method of expanding a casing diameter downhole utilizing a hydraulic expansion tool. U.S. Pat. No. 6,021,850 discloses a downhole tool for expanding one tubular against a larger tubular or the borehole. Publication U.S. 2001/0020532 A1 discloses a tool for hanging a liner by pipe expansion. U.S. Pat. No. 6,050,341 discloses a running tool which creates a flow restriction and a retaining member moveable to a retracted position to release by the application of fluid pressure.
Due to problems with the procedure and tools used to expand a smaller diameter tubular into reliable sealing engagement with a larger diameter tubular, many tools have avoided expansion of the tubular and used radially expandable seals to seal the annulus between the small diameter and the large diameter tubular, as disclosed U.S. Pat. No. 5,333,692. Other patents have suggested using irregularly shaped tubular members for the expansion, as disclosed in U.S. Pat. Nos. 3,179,168, 3,245,471, 3,358,760, 5,366,012, 5,494,106, and 5,667,011. U.S. Pat. No. 5,785,120 discloses a tubular patch system with a body and selectively expandable members for use with a corrugated liner patch. U.S. Pat. No. 6,250,385 discloses an overlapping expandable liner. A sealable perforating nipple is disclosed in U.S. Pat. No. 5,390,742, and a high expansion diameter packer is disclosed in U.S. Pat. No. 6,041,858.
Various tools and methods have been proposed for expanding an outer tubular while downhole, utilizing the hydraulic expansion tool. While some of these tools have met with limited success, a significant disadvantage to these tools is that, if a tool is unable to continue its expansion operation (whether due to the characteristics of a hard formation about the tubular, failure of one or more tool components, or otherwise) it is difficult and expensive to retrieve the tool to the surface to either correct the tool or to utilize a more powerful tool to continue the downhole tubular expansion operation. Accordingly, various techniques have been developed to expand a downhole tubular from the top down, rather than from the bottom up, so that the tool can be easily retrieved from the expanded diameter bore, and the repaired or revised tool then inserted into the lower end of the expanded tubular.
The disadvantages of the prior art are overcome by the present invention, and an improved system for forming a patch in a well and a location along the downhole tubular string which has lost sealing integrity is hereafter disclosed. The system includes a tubular patch with a central patch body, an upper expander body, and a lower expander body, and a running tool with a top expander and a bottom expander to move the tubular patch into sealing engagement with the downhole tubular string. The present invention also discloses a tubular expansion running tool and method which may be reliably used to expand a downhole tubular while facilitating retrieval of the tool and subsequently reinsertion of the tool through the restricted diameter downhole tubular.
A system for forming a patch in a well includes a tubular patch for positioning within the downhole tubular string at a location that has lost sealing integrity. The tubular patch is supported on a running tool suspended in the well from a work string. The tubular patch includes a central patch body having a generally cylindrical central interior surface, an upper expander body having a generally cylindrical upper interior surface and an upper exterior seal, and a lower expander body having a generally cylindrical lower interior surface and a lower exterior seal. The tubular patch may also include an expansion joint positioned between the upper expander body and the lower expander body to compensate for expansion and contraction of the tubular patch caused by thermal variations between the tubular patch and the tubular string exterior of the patch. The running tool includes an inner mandrel that is axially movable relative to the central patch body, and one or more pistons each axially movable relative to the inner mandrel in response to fluid pressure within the running tool. A top expander is axially moveable downward relative to the upper expander body in response to axial movement of or one or more pistons, and a bottom expander axially moves upward relative to the lower expander body in response to axial movement of the one or more pistons. The one or more pistons preferably includes a first plurality of pistons for moving the top expander relative to the upper expander body, and a second plurality of pistons for moving the bottom expander relative to the lower expander body. Each of the upper expander body and lower expander body may include a set of slips for gripping engagement with the inner surface of the tubular string.
It a feature of the present invention that the lower expander includes a first plurality of axially-spaced expander segments and a second plurality of axially-spaced expander segments. Each of the second plurality of expander segments is spaced between adjacent first expander segments and is axially movable relative to the first expander segments. When the first and second plurality of expander segments are vertically aligned, the expander segments together expand the lower expander body as they are moved upward through the lower expander body. When the first expander segments are axially spaced from the second expander segments, the expander segments of the running tool may be passed through the central patch body for purposes of installing the running tool on the tubular patch and for retrieving the running tool to the surface after setting of the tubular patch.
It is a feature of the present invention that an outer sleeve interconnects a first plurality of cylinders to the top expander, and that a shear member may be provided for interconnecting the outer sleeve and the running string.
A related feature of the invention is that another shear member may be provided for disconnecting the first plurality of pistons and the top expander after a selected axial movement of the top expander relative to the upper expander body.
It is a feature of the invention that exterior seals may each be formed from a variety of materials, including a graphite material.
It is another feature of the invention that an expansion joint may be provided between the upper expander body and the lower expander body for thermal expansion and/or contraction of the central patch body.
Still another feature of the invention is that the running tool may be provided with a plug seat, so that a plug landed on the seat achieves an increase in fluid pressure within the running tool and to the actuating pistons.
Another significant feature of the present invention is that a running tool and method are provided for expanding a downhole tubular while within the well. Hydraulic pressure may be applied to the tool to act on the lower expander to either expand an outer tubular, or to expand the lower expander body of the thermal patch. The expander members may be positioned between axially aligned positions for expanding the downhole tubular and axially separated positions for allowing the expander members to collapse allows the running tool to be easily retrieved to the surface.
Yet another feature of the invention is that a plurality of dogs or stops may be provided on the running tool for preventing axial movement of the upper expander body in response to downward movement of the upper expander, and axial movement of the lower expander body in response to upward movement of the lower expander. The dogs may move radially inward to a disengaged position for purposes of installing the running tool on the tubular patch and for retrieving the running tool after installation of the tubular patch. Each of a plurality of dogs may be biased radially outward to an engaged position within the controlled gap of the expansion joint.
It is a significant advantage that the system for forming a patch in a well according to the present invention utilizes conventional components with a high reliability. Also, existing personnel with a minimum of training may reliably use the system according to the present invention, since the invention relies upon utilizing well-known surface operations to form the downhole patch.